Prior art pressure-test plug tools for testing the pressure integrity of pressure control stacks on wellheads are well known in the art. The pressure-test plug tools are used to test the pressure integrity of control stack components such as blowout preventers, valves, tees, etc., and joints between the components prior to drilling or stimulating a well.
While most prior art test plug tools are known to function well, they all suffer from a drawback in that they are only designed to test the pressure integrity of the stack above a casing joint, i.e., above a connection between a casing and a casing support. With prior-art devices, the pressure integrity of the casing joint cannot be verified. During well stimulation operations, where fluid pressures may spike to 20,000 PSI, this joint may be susceptible to leakage and/or failure, resulting in expensive repairs, cleanup, downtime and potential environmental damage.
Many configurations for pressure-test plug tools have been invented. For example, in U.S. Pat. No. 5,775,422 (Wong et al.) entitled TREE TEST PLUG, the test plug is lodged within the tubing hanger, i.e., above the connection between the surface casing and the wellhead. In this configuration, the pressure integrity of the stack beneath the tubing hanger cannot be verified.
In U.S. Pat. No. 4,121,660 (Koleilat) entitled WELL PRESSURE TEST PLUG, the test plug is seated in the bore of the wellhead. With the test plug in this configuration, the pressure integrity of the wellhead-to-casing joint cannot be tested.
Similarly, in U.S. Pat. No. 4,018,276 (Bode) entitled BLOWOUT PREVENTER TESTING APPARATUS, the test plug is positioned in the bore of the wellhead. The position of the test plug permits pressure-testing of the blowout preventer but does not permit pressure-testing of the wellhead or the casing connection.
Likewise, in U.S. Pat. No. 3,897,824 (Fisher) entitled BLOWOUT PREVENTER TESTING APPARATUS, the test plug is positioned in the bore of the wellhead beneath the blowout preventer. With the test plug in this location, it is not possible to verify the pressure integrity of the lower part of the wellhead, such as the joint between the wellhead and the well casing.
In U.S. Pat. No. 3,177,703 (Waters et al.) entitled METHOD AND APPARATUS FOR RUNNING AND TESTING AN ASSEMBLY FOR SEALING BETWEEN CONDUITS, the test plug is positioned in the bore of the wellhead above the joint between the wellhead and the casing. With the test plug in this location, it is not possible to pressure-test the wellhead-casing joint.
In U.S. Pat. No. 2,951,363 (Diodene) entitled TOOL FOR TESTING WELL HEAD EQUIPMENT, the test plug is also positioned above the wellhead and casing joint. Pressure-testing of the casing joint is not possible with the test plug located in that position.
There therefore exists a need for a test plug tool for pressure-testing wellhead control stacks that permits testing of the pressure integrity of a casing joint, i.e., the joint between a surface casing and a wellhead, the joint between an intermediate casing and an intermediate casing mandrel, or the joint between a production casing and a production casing mandrel.